downwelling


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downwelling

[′dau̇n‚wel·iŋ]
(oceanography)
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By rough estimation the downwelling irradiance just under the water surface (immediately after refraction) [E.sub.d,PAR] (z = -0) = 0.934 [E.sub.d,PAR] (z = 0), because it is supposed that the reflection coefficient from water surface is approximately 0.066 (Jerlov, 1976).
Upon stimulation with different intensities of light in the apparatus that simulated the natural underwater angular light distribution, larvae displayed only positive phototaxis toward downwelling light (Fig.
Reynolds (1997), when presenting theories and hypothesis related to the succession and development of phytoplankton populations in pelagic environments, emphasises the importance of the matrix of possibilities related to the distribution of downwelling irradiance and limiting nutrient concentration in relation to mixed depth represented by temperature distribution and algal growth supporting capacity.
Juvenile growth was correlated with an atmospheric forcing index and immature growth was correlated with the amount of coastal precipitation, but the magnitude of winter and spring coastal downwelling in the Gulf of Alaska and the Pacific Northwest atmospheric patterns that influence the directional bifurcation of the Pacific Current were not related to the growth of Karluk sockeye salmon.
Experiments in 1995 and 1996 show that such sequences of upwellings can often take place, because up-and downwelling usually mirror each other at the opposite coasts.
This volume is attractively packaged and published by the Alaska Sea Grant College Program, although it is a shame that several beautifully drafted diagrams in the introductory chapter, showing oceanographic features such as downwelling and seasonal changes in current flow, could not be published in color.
In addition to the eddy covariance variables, we measured downwelling photosynthetically active radiation (LI- 190, LI-COR, Lincoln, Nebraska), downwelling solar radiation (LI-200, LI-COR, Lincoln, Nebraska), air temperature at 0.2, 0.5, 1.0, 2.0, and 4.0 m (0.2 mm thermocouples), soil temperature at 0.05 and 0.3 m (I mm thermocouples), horizontal windspeed at 2 and 4 m (Model 2010, Weathermeasure, Sacramento, California), and surface radiative temperature (Model 4000, Everest Interscience, Fullerton, California).
In his view, crustal material is dragged into a convergence zone over a downwelling, piles up, and undergoes a great deal of deformation.
In the model simulations, as rock at the top of the mantle cools, it sinks until it reaches the 670 km boundary, Initially, the cooler, downwelling rock is not dense enough to sink into the lower mantle, so it pools right above the boundary Eventually, however, the puddle of cooler rock grows heavy enough to break through the boundary and cascade into the lower mantle, flowing toward the core.
In particular, the picture implies a downwelling under North America and an upwelling originating at the core-mantle boundary under northwest Africa.
We suspect that the underlying cause for the difference in downwelling frequency is due to the strength of the Pacific high: anomalies in SLP one day before a typical wind relaxation event began are only ~2 hPa (Fewings et al.